Patent GB-1063025-A (GB)
Title: Multistep coating technique for piezoelectric and magnetostrictive materials
IPC: B05D1/02
Filed: 1964-05-01
Abstract: 1,063,025. Coatings; coating apparatus. ESSO RESEARCH & ENGINEERING CO. May 1, 1964 [July 2, 1963], No. 18196/64.Headings B2K and B2L. A method of applying to a piezoelectrically or magnetostrictively responsive material a liquid substance capable of forming a coating on the material and enabling its use as a detection device in analysis, comprises directing atomized droplets of the liquid onto the surface of the responsive material at periodic intervals in a plurality of spray pulsations, thus forming a plurality of layers of the liquid substance on the material. The responsive material may be a piezoelectric crystal and only a certain preselected portion of the crystal may be coated e.g. a portion of each side of the crystal may be coated by applying 6 to 100 layers of liquid to form the solid coating. The coating is normally a liquid; a solution of a solid material in a suitable solvent in which case the deposit of each spray pulsation is allowed to dry completely before the next spray pulsation is applied the solvent being readily volatile at ambient temperature and pressure; a dispersion of a solid material in a suitable liquid; or a colloidal dispersion of a solid material in a suitable soluble dispersing medium. The liquid or solid material has the ability to interact with the particular substances to be detected. The liquid substance may comprise from 0.08 to 20 gram of a non cross linked sodium salt of a sulphonated polystyrene having a molecular weight of from 5000 to 10,000,000 (Staudinger) prior to sulphonation per 100 ml. of water. The droplets may be directed onto the crystals for a time of from 0.05 to 10 seconds and the interval of time between the formation of each layer is from 1 to 60 seconds. The liquid substance may be filtered prior to atomization to remove particles contained therein having a larger size than the total thickness of coating on either side of the crystal. Apparatus for coating a piezoelectrically or magnetostrictively responsive material comprises a main holder having a base member 1 and upright support member assembly 2 mounted on the base, an atomizer assembly a fluid well 8 containing the sprayable coating substance a responsive material holder 15 and a supporting rig 24 for the holder. The apparatus may also comprise timing means 13, 13A to control the frequency of atomization. The atomizer assembly may contain an airbrush 5. The holder may comprise a rod 16 having a block 17 affixed to one terminal thereof, a crystal socket 18 affixed to the block for removably inserting a crystal of responsive material, stencil plates 20, 21 rotatably mounted on the block and a control for adjusting the block. The rig 24 may comprise a base member 25 having two upright spaced supports 26, 27 connected thereto, holders positioned on the supports and adapted to permit free rotation of the rod of the holder clamps located on the supports and adopted to hold the rod in fixed position, and orienting means to maintain the responsive material perpendicular to the path of the sprayed coating material.